End labels coated with heatsealable adhesives



Nov. 19, 1968 P. A, USSBAUMER ET AL 3,411,701

END LABELS COATED WITH HEAT-SEALABLE ADHESIVES Filed Jan. 50, 1967 INVENTORS PHILIP A ussanumen BY (names mesJouusoN A-rrvs.

United States Patent 3,411,701 END LABELS COATED WITH HEAT- SEALABLE ADHESIVES Philip A. Nussbaumer and Charles James Johnson, Dallas,

Tex., assignors to St. Regis Paper Company, New York, N.Y., a corporation of New York Continuation-impart of application Ser. No. 339,237,

Jan. 21, 1964. This application Jan. 30, 1967, Ser.

7 Claims. (Cl. 22987) ABSTRACT OF THE DISCLOSURE Labels for sealing the overlapping end flaps of an overwrapped package are coated with a film of a heat-scalable adhesive composition, which labels, when applied to the package adhere more tenaciously to the outermost flap than to the underlying flaps. In the area of the label that corresponds to the outermost flap, the film of the adhesive composition is heavier or thicker than on the other area, or the film has a different composition than the film in the other area.

This application is a continuation in part of our prior application No. 339,237, filed January 21, 1964 now abandoned.

The present invention pertains to adhesive-coated end labels for use in bonding or adhering together the foldedover end flaps of overwrappers that are used in the packaging of commodities, particularly perishable commodities, or cartons or cases containing commodities.

The back or rear surfaces of end labels of the type to which the present invention is directed are coated or covered with :a nontacky film of a substance which is usually referred to as a hot-melt or heat-sealable adhesive, which does not, however, become tacky or adherent to a substrate until it is heated or melted. It thus differs from plain labels or the more-common labels whose rear surfaces are provided with a film of dextrin, glue, or other remoistenable adhesive composition.

The term package is used herein to refer specifically to a solid commodity, particularly a perishable commodity (such as a loaf of bread or other foodstuff), or a plurality of such commodities, or a carton or case containing such a commodity or commodities, that has been enclosed in or covered (that is, overwrapped) with a flexible printed or transparent sheet material or wrapper whose overlapping edges have been adhered or bonded together to impede the transmission of water vapor into or from the package. The sheet material that is used for overwrapping the commodity or commodities to produce such a package is referred to herein as an overwrap or overwrapper.

The adhesive film or coating on the back or rear surface of end labels of the present invention, which is that surface of the label that is adhered to the folded-over end flaps of the overwrapper that had previously been bonded together to form a sealed package, includes an area or portion which, after the adhesive film has been activated by heat, is capable of adhering more firmly or tenaciously than the remaining portions of the adhesive film to surfaces of sheet materials to which the end label is applied, so that the greater portion (but not all) of the end label, may be readily peeled or separated without tearing the underlying or substrate sheet material. This characteristic distinguishes the end labels of the present invention from prior end labels in which all areas of the adhesive film had identical adhesion characteristics.

In a preferred embodiment of the present invention, the greater or more-readily peelable portion of the end label is covered with a film of a conventional so-called delayed-tack adhesive composition, or such as are de- 'ice scribed in the copending application of Hardy G. Lohse, Ser. No. 488,280, filed Sept. 17, 1965, so that, when the package is opened and a portion of its contents are withdrawn, the end flaps of the overwrapper can be refolded in new or different positions or locations and be stuck and held together with the original end label whose peela'ble adhesive surface retains much or at least some of the tackiness that was developed when the end label was originally applied, thereby continuing at least partially to protect the remaining contents of the package. End labels coated with films of such delayed-tack adhesive compositions are especially desirable for producing packages consisting of overwrapped whole or sliced loaves of bread and similar perishable articles of food, the entire contents of which normally are not consumed or used :at one time.

In the automatic machines that are presently used for packaging loaves of bread and similar perishable commodifies, the commodity is first generally encircled or surrounded by a sheet of a flexible wrapping material whose width is greater than the length of the loaf or commodity that is to be packaged. The edges of the sheet material which are thus brought together, generally into overlapipng position at the bottom or underside of the loaf or package, and which are referred to herein as the longitudinal edges, are bonded together by means of a heated plate with which the package comes into contact as it advances progressively through the machine. Each of the two side or lateral edges of the sheet material, which extend outwardly in different directions from the loaf or commodity that is to be packaged, are then pressed inwardly and folded by means of so-called fingers of the machine to form four overlapping flaps that are likewise bonded to each other by being brought into contact with appropriately placed heated plates. Normally in this folding operation, one of the side flaps is first folded inwardly, after which the top flap is folded downwardly and inwardly to overlap that side flap, then the second flap is folded inwardly, and finally the bottom flap is folded upwardly and inwardly to overlap at least portions of the three other overlapping flaps. End labels are then applied and adhered by means of heat toeach of the thus-sealed ends of the package.

End labels applied to such packages serve to protect the package from being opened inadvertently during handling; they may also be printed to provide brand identification, price, and other suitable information with respect to the contents of the package. When end labels are used, the end flaps of the package need not be bonded or adhered to each other as tenaciously as would normally be required to produce a sealed package having no end labels.

The package to which the end labels of the present invention are intended to be applied is illustrated in the accompanying sheet of drawings, of which FIG. 1 represents a package containing :a loaf of bread, one end of which has been partially unfolded to show an end label still attached to the fourth or last flap that was folded over to close the package,

FIG. 2 represents the rear surface of an end label containing the adhesive film, and

FIG. 3 represents the rear surface of an alternative form of end label.

The sequence or order in which the end flaps of the package are folded inwardly to close the package can be better visualized by reference to FIG. lof the drawings. The side flap 12 of the package is first folded inwardly, while the top flap 13, the second side flap 14, and the bottom flap 15 are each then successively folded inwardly.

The end label 22 which is represented in FIG. 2 contains an adhesive film 23 that covers the greater portion of the rear surface of the end label. The portion of the end label and adhesive film that is designated 24 is an area which is slightly smaller than the exposed surface area of the bottom flap of the package represented in FIG. 1, the boundaries of which flap are represented in projection upon FIG. 2 by the broken line enclosing the area 25. The area 24 that is represented in FIGS. 2 and 3 is smaller than the flap 15 so that the stronger adhesive will not overlap any of the other flaps, as it would if the area 24 covered the entire area of flap 15 and the label were applied to that end of the package slightly out of register with that flap, or the dimension of the flap varied slightly from package to package, as they normally do.

The regions 26 and 27 of the alternative end label that is represented in FIG. 3 are uncoated areas that have not been covered with the adhesive film. These uncoated areas serve two purposes; namely, they provide a region in which the label can be more readily gripped with the fingers and peeled from the package to which it is applied, and it also makes it possible to cut or sever the labels from a web with a knife without contact of the knife with the adhesive film, thereby obviating the soiling of the knife blade with the adhesive composition and the soiling of the edges of the labels that were cut with the thus soiled knife blade.

Sheet materials that are generally used as overwrappers for bread and similar perishable commodities to produce sealed packages include such diverse sheet materials as heat-scalable polyolefin resins, such as polyethylene and polypropylene resins, as well as composite sheets of these resins and sheets or layers of resins, cellophane sheet materials at least one surface of which has been coated with a nitrocellulose or other heat-scalable film of layer of hot-melt adhesive, and common waxed papers coated with normal hot-melt adhesives. Such overwrappers, when bonded by heat at their overlapping portions, provide sealed packages in which bread and similar perishable commodities will retain their freshness for long periods.

The end labels that are referred to herein are made from a normal paper label stock although they can be made of other suitable sheet materials.

Because of the more tenacious adherence of a portion of the end label of the present invention to the outermost of the four superimposed flaps, that flap may be easily peeled away together with the end label from the underlying flaps, thereby facilitating the opening of the package. If the outermost flap was not more tenaciously bonded to the end label than the other flaps, it is apparent that, when the label was peeled away from the package, the entire label would be released, and the end label would peel away from the outermost flap just as easily as from the underlying flaps and that, when that occurred, another peel would be required to separate the outermost flap from the underlying flaps.

As hereinbefore stated, the rear surface of the end labels of the present invention includes an adhesive film in the area 24 which, after activation by heat, adheres more firmly to the folded-over end flaps of the package than the adhesive film in the area 23 of the end labels. Such films having differing adhesive characteristics may be produced in accordance with the present invention by the use of different adhesive compositions or by the use of different amounts of the same adhesive composition.

In accordance with the first of the foregoing alternatives, the two different adhesive compositions are applied to the end label in two separate coating operations. For example, the two adhesive films are applied by the use of two different gravure rolls from which rolls they are transferred and applied to different areas of the end label.

In accordance with the second alternative method, which is a preferred embodiment of the present invention, the film of the adhesive composition is applied in a single operation by using a gravure applicator roller (or roll) from different areas of which different quantities of the adhesive composition are transferred and applied to different areas of the end label. For example, the gravure roll can be engraved with a pattern of so-called quadrangular cells formed from crossing relieve or raised lines, from which roll the adhesive composition is transferred from the intagli-o or depressed portions or cells. Since conventional applicator rolls are generally engraved so that the depth of each individual cell is greater as the number of cells per linear inch of the engraved area of the roll decreases, an area engraved with 55 cells per linear inch, each having a depth of 0.0065 inch, which are conventional dimensions, will transfer approximately 20 percent more liquid than an area engraved with cells per linear inch, each having a depth of 0.0054 inch, which are also conventional dimensions. However, when the liquid to be transferred is a viscous material, as are the heat-scalable adhesive compositions of the present invention, approximately twice as much adhesive composition is transferred from the area engraved with 55 cells per inch than is transferred from the area engraved with 75 cells per inch.

For applying each of the adhesive compositions that are described in the examples which follow, the roll which was used was a roll that was engraved with 55 quadrangular cells per inch having a depth of 0.0065 inch in the area corresponding to the area of stronger adhesion of the end label, and engraved with 75 quadrangular cells per inch having a depth of 0.0054 inch in the remaining area of the end label.

The adhesive film on end labels which were coated by use of the foregoing roll and with the heat-scalable adhesive composition described in Example 1 hereinafter, had a thickness equivalent to 14 pounds per ream (3000 square feet) on the stronged adhering area and a thickness equivalent to only 7 pounds per ream on the remaining coated area. The adhesive composition of Example 1 produces a peelable coating when applied in a thickness equivalent to not more than 8 pounds per ream; substrates that have been bonded with a greater thickness of the adhesive composition normally cannot be sepaarted without tearing of the label, the overwrapper, or both.

In the examples which follow, the adhesive compositions were applied to the label "by means of the foregoing gravure roll. The coated end label was then applied to the ends of a sealed package that had been overwrapped with a sheet of the specified wrapping material in such a manner that the stronger adhering area of the label was bonded to the fourth or outermost flap of the overwrapper.

The different temperatures of the heated plates that were used are specified in each example. In all examples, the end label was maintained at the specified temperature by contact with the heated plate for a period or dwell time of 3 seconds. The package with the attached end label was then allowed to cool to the ambient room temperature and the overwrapped ends of the package, including the label, were cut from the package.

The relative adhesion or seal strength of the various areas of the end label to the underlying flaps of the overwrapper as well as the relative adhesion of the flaps to each other was determined in accordance with a method and with an instrument similar to that described by Anthony Kinsel and Hans Schindler in an article entitled Adhesion Test for Microcrystalline Wax that was published in Paper Trade Journal, vol. 128, No. 5, pages 18 to 20 (Feb. 3, 1949). The instrument is referred to as a Suter tester or single strand strength and elongation tester and is available from Alfred Suter Co., 200 Fifth Avenue, New York, New York 10010. In this test, the relative adhesion is measured by determining the force in grams per linear inch that is required to separate or peel a specimen of the coated end label from the various flaps of the overwrapper to which it is attached and the individual successive flaps from each other in the following manner:

In this relative adhesion test, the ends of the two adhering sheets between which the relative adhesion is to be determined are clamped between the jaws of the two clamps of the Suter tester and the two sheets are then pulled apart from each other, at a constant rate of pull that is applied to the two clamps to which the two sheets are attached by means of a hydraulic brake consisting of a piston moving inside a cylinder filled with oil.

The constant rate of pull that was used in the tests that are described herein was 12 inches per minute and this pulling force was applied between the clamps in such manner that the two surfaces were pulled apart at an angle of 180, namely, in directions parallel to each other.

A relative adhesion value between 150 and 400 grams per inch in this test indicates satisfactory adhesion or performance of the adhesive compositions. At lower values, the surfaces are not bonded to each other firmly enough and, at values of 500 grams per inch and more, which represents a tear seal, the surfaces are not readily peelable from each other without tearing.

The relative adhesion of the various surfaces to each other are referred to in the examples which follow in the following order:

The surfaces are referred to by the numerals used in designating the areas or flaps of which they are a part in the accompanying drawing and these single numerals (1 to 5) will be used hereinafter to refer to these pairs of adhering surfaces in the tables which follow:

(1) End label area 24 to flap 15,

(2) End label 23 to flaps 12, 13, and 14,

(3) Flap to flap 14,

(4) Flap 14 to flap 13, and

(5 Flap 13 to flap 12.

Example 1 A heat-sealable adhesive composition consisting of a mixture of 5 parts by weight of a microcrystalline wax having a melting point of 145-155 F. and 35 parts by weight of a copolymer of ethylene and vinyl acetate, which is sold under the trade name Elvak by E. I. du Pont de Nemours and Co., Wilmington, Del., was used to coat a paper label stock with the engraved roll described hereinbefore. When paper end labels coated with films of this ad hesive composition in the manner described hereinbefore were applied at a temperature of 230 to 250 F. to the end flaps of a loaf of bread that was overwrapped in a conventional bread-wrapping machine with a polyethylene sheet, the following relative adhesion results were obtained in accordance with the test described hereinbefore:

Relative adhesion.

Surface pair: grams per inch 1 (tear seal) 500 2 300 3 250 4 200 .5 0

Example 2 Using the same labels that are described in Example 1, but applying them at a temperature of 300 F. to the end flaps of a loaf of bread overwrapped in a conventional bread-wrapping machine with a nitrocellulose-coated cello- 6 phane sheet (Du Pont 210-MSD 60), the following relative adhesion results were obtained:

Relative adhesion,

Surface pair: grams per inch Example 3 Using end labels that had been coated as described hereinbefore with a heat-sealable adhesive composition consisting of parts by weight of a low-molecularweight polyethylene resin which is sold under the tradename Epolene C by Eastman Chemical Products, Inc., Chemicals Division, Kingsport, Tenn. and 20 parts by weight of a polyterpene resin which is sold under the tradename Piccolyte by Pennsylvania Industrial Chemical Corporation, and applying them at a temperature between 250 and 280 F. to the end flaps of a loaf of bread overwrapped in a sheet of the same polyethylene that was used in Example 1, the relative adhesion results that were obtained were essentially identical to those obtained with the materials specified in Example 1.

Example 4 Using labels that had been coated as described hereinbefore with a heat-sealable adhesive composition consisting of 20 parts by weight of parafiin wax having a melting point of 165 C., 40 parts by weight of a pentaerythritol ester of rosin which is sold under the trade name Pentalyn by Hercules Incorporated, Wilmington, Del., and 40 parts by Weight of the same copolymer of ethylene and vinyl acetate that was specified in Example 1 hereinbefore, and applying them at a temperature between 250 and 280 F. to the end flaps of a loaf of bread overwrapped in a sheet of cast unoriented polypropylene, the following relative adhesion results were obtained:

Relative adhesion,

Surface pair: grams per inch EXAMPLE 5 Paper end labels were coated as described hereinbefore with films of a delayed-tack adhesive composition consisting of a mixture prepared by melting together 70 parts of dicyclohexyl phthalate and 30 parts of sucrose benzoate and stirring the molten mixture vigorously at a temperature of F. into a mixture of two aqueous emulsions of thermoplastic copolymers, the mixture of emulsions consisting of 40 parts by weight of an emulsion containing 40 percent by weight of a thermoplastic copolymer of vinylpyrrolidone and ethyl acrylate in the ratio of 60 parts by weight of vinylpyrrolidone to 40 parts by weight of ethyl acrylate and an anionic emulsifying agent, such as is sold under the tradename Polectron by General Aniline and Film Corporation of New York, N.Y., and 10 parts by weight of an aqueous emulsion containing 45 percent by weight of a thermoplastic copolymer of styrene and butadiene in the ratio of 80 parts by weight of styrene to 20 parts by Weight of butadiene and a nonionic emulsifying agent, such as is available under the trade designation Dow 859 from Dow Chemical Company of Midland, Mich.

he resulting end labels, when applied at a temperature above about 220 F. to end flaps of loaves of bread overwrapped with conventional sheet wrapping materials such as are referred to herein, and particularly to those specified in the foregoing examples, give relative adhesion results similar to those included in the foregoing examples. However, when such labels are peeled from the end flaps of such a package, the adhesive film retains its tackiness for long periods and the package can be rescaled with the same tacky label without the application of heat.

Inasmuch as the foregoing disclosure comprises preferred embodiments of the invention which were selected only for purposes of illustration, it is to be understood that the invention is not restricted thereto and that modifications and variations may be made therein without departing from the invention, whose scope is restricted only as defined in the appended claims.

We claim:

1. A label that is adapted to be applied over a plurality of successively folded-over end flaps of a package consisting of an article overwrapped with a sheet of flexible wrapping material, one surface of which label is substantially completely covered by an essentially continuous layer of a heat-sealable adhesive composition, which layer includes an area that is adapted to overlap a substantial portion of the area of the outermost flap at either end of the overwrapped package and which area of the adhesive composition, when the entire layer of the adhesive composition is activated by heat, adheres more tenaciously to the outermost underlying flap than does the remaining area of the essentially continuous layer of the adhesive composition to the remaining flaps, so that the end label together with the adherent outermost underlying flap can be peeled more readily from the remaining underlying flaps in opening the package.

2. A label as defined in claim 1 in which the essentially continuous layer of the heat-scalable adhesive composition is thicker at the area that is to adhere to an outermost flap of the package.

3. A label as defined in claim 1 in which each of the two areas of the essentially continuous layer of the heat-sealable adhesive composition is covered with a different heat-sealable adhesive composition which compositions differ from each other with respect to their adhesion characteristics.

4. A label as defined in claim 1 in which the heatsealable adhesive composition is a delayed-tack adhesive composition, areas of which label, after the label has been applied to the folded-over flaps at an end of the package, can be reused, because of the tackiness remaining in the layer of the adhesive composition, to reattach the label without application of heat to the same or new flaps formed from the overwrapper, and thereby reseal the package.

5. A label as defined in claim 1 in which the continuous layer of the heat-sealable adhesive composition does not extend into one or more of the marginal areas of the label so that the label can be more readily grasped at such an unattached marginal area and peeled from the package.

6. A package consisting of an article overwrapped with a flexible sheet material at least one end of which is closed by a plurality of successively folded-over flaps of the sheet material together with an adhering end label as defined in claim 1, which end label together with the adherent outermost underlying flap can be peeled more readily from the remaining underlying flaps than from the outermost underlying flap in opening the package.

7. A package as defined in claim 6 in which both opposite ends of the package are each closed by a plurality of folded-over flaps of the sheet material together with an adhering end label.

References Cited UNITED STATES PATENTS 2,818,169 12/1957 Bergstedt i 22948 2,975,091 3/1961 Tobey 117122 3,140,809 7/ 1964 H-ickin et al 22937 FOREIGN PATENTS 883,408 11/ 1961 Great Britain.

DAVIS T. MOORHEAD, Primary Examiner. 

